Comparative analysis between traditional topology optimization and lattice structure optimization for additive manufacturing

Structural weight reduction is gaining significance as engineering applications seek to increase the strength-to-weight ratio in their designs. Both lattice structures and topology optimization provide different avenues for achieving weight reduction in mechanical systems. However, comparisons between these methods are rarely conducted when both are subject to the same constraints. A controlled numerical comparison of six lattice geometries, three strut-based (BCC, FCC, Graph-Diamond) and three TPMS-based (Gyroid, Schwarz, Diamond), with a single topology optimized solid was undertaken, all constrained within a design volume of 113 × 20 × 20 mm3 and to the same total mass of approximately 60g of Ti-6Al-4V. Convergence of mesh size was investigated for each structure, and all models were subjected to identical tensile boundary conditions using linear elastic finite element analysis. The topology optimization process used a compliance-minimizing formulation, with the design load selected based on the maximum tensile capacity observed among the lattice specimens.The results clearly indicate that the internal geometry of each of the structures has a direct effect on tensile behaviour. The strut-based lattices have shown significant bending effects and rapid stress localization, leading to failure loads ranging from approximately 7 kN to 20 kN. The TPMS-based geometries have provided a more even distribution of stress and increased capacity compared to the strut-based geometries, with the TPMS "Diamond" geometry capable of supporting loads up to approximately 33.5 kN before approaching the yield strength of the material. The topology-optimized solid had superior tensile properties to all of the lattice geometries, supporting elastic deformation loads of up to 82.5 kN - nearly twice the capacity of the strongest lattice structure, despite being subject to the same total mass constraint. The data demonstrate that the presence of continuous and unbroken load paths can provide a significant mechanical advantage when subjected to tensile loading, and highlight the importance of optimizing geometries in order to produce optimal designs for components to be produced through additive manufacturing.